Immortalization of hepatic progenitor cells

Area of Science:

• Hepatology
• Stem Cell Biology
• Regenerative Medicine

Background:

• Orthotopic liver transplantation is limited by donor organ shortage, impacting treatments for liver failure and inherited metabolic diseases.
• Terminally differentiated hepatocytes have limited in vitro expansion capacity, necessitating alternative cell sources like hepatic stem cells.
• Fetal hepatic cells possess properties that may overcome limitations of adult hepatocytes, but require methods for in vitro expansion without losing differentiation potential.

Purpose of the Study:

• To develop a method for in vitro expansion of primate hepatic progenitor cells without compromising their differentiation potential.
• To investigate the engraftment, proliferation, and differentiation capacity of immortalized hepatic progenitor cells in vivo.
• To establish a controllable immortalization strategy for hepatic progenitor cells for potential cell therapy applications.

Main Methods:

• Immortalization of a primate hepatic progenitor cell clone using a retroviral vector encoding SV40 Large T antigen flanked by lox P sites.
• Assessment of bipotency by analyzing hepatocytic and biliary lineage markers.
• Transplantation into athymic mice to evaluate engraftment, proliferation, and differentiation.
• Induction of cell death/cessation of proliferation via CRE recombinase-mediated excision of the SV40 Large T transgene.

Main Results:

• The immortalized hepatic progenitor cells were bipotent, expressing markers for both hepatocytic and biliary lineages.
• Approximately 50% of transplanted immortalized cells engrafted in mice, ceased proliferation, and differentiated into adult hepatocytes.
• SV40 Large T antigen-dependent immortalization was confirmed, as CRE recombinase expression led to growth arrest and cell death.
• The hepatic microenvironment appears to play a crucial role in regulating cell engraftment and differentiation.

Conclusions:

• A method for immortalizing primate hepatic progenitor cells while retaining differentiation potential has been established.
• These immortalized cells can engraft and differentiate into functional hepatocytes in vivo, suggesting their therapeutic potential.
• Controllable immortalization offers a promising strategy for expanding hepatic progenitor cells for cell therapy of liver diseases.
• Further studies are warranted to analyze the fate and therapeutic efficacy of these cells in animal models.